Some kind of a simple implantation of teeth in the mouth is known from the Pharaoh's ancient times. Modern dental surgical tooth implantation are extremely efficient. Various embodiments of oral implants are known, these commonly including a tubular body consisting of a smooth head and a cylindrical or cylindro-conical rod intended to be screwed or inserted by compaction into an osseous volume drilled beforehand using a tap. The firsts ancient osseointegration techniques was poor and the attachments for the implants in the jaw bone were purely mechanical and were not as successful as the present techniques that rely on osseointegration. However, it is known that before osseointegration, it was not necessary to wait for prolonged time periods until integration was completed. Some known prior art provides the means for attachment of an implant to the jaw bone structure by means of pins that are forced laterally out from the implant after the implant is inserted in the bone. These pins have pointed ends that, with application of high force, penetrate the bony structure, i.e., the softer spongiosa of the jaw bone, in an effort to make a tooth implant permanent. However, the spongiosa is a relatively soft, living bony material, and subject to changes. Accordingly, reliability and permanence of an implant were not assured. Another known procedure of the missing tooth replacement is to open the gum and to embed an implant in the bone structure beneath the gum. The implant is held in the bone in a socket hole by friction or the implant may be threaded into the bone. The gum is then closed over the implant and heals. When a proper material is used for the implant, e.g., titanium, the bone grows into the implant by osseointegration so that after several months the implant becomes a part of the bone structure in the mouth. The procedures, which are followed after osseointegration has advanced, depends upon the dental practitioner's selection of a manufacturer's product. The mentioned above complete systems of dental implants and prostheses for subsequent attachment to the implants are well known and described, for example, a system that is widely used by dental practitioners is available from Nobelpharma USA Inc., Westmont, Ill. In one system, the implant in a typical construction has an axially threaded hole at its top, i.e., the proximal end near the gum. After the bone has joined to the implant, the gum over the implant is reopened to expose the tapped hole. Then, an abutment is threaded into the tapped hole of the implant and extends to a level above the gum. The protruding end of the abutment is constructed with a non-round shape for attachment of a prosthesis. Also, the protruding end includes a central threaded hole extending inward toward the jaw bone. A false tooth or crown is provided with a hole, known as a chimney, therethrough, and a non-round recess in its base that corresponds in shape to the protruding non-round cross-section of the abutment. Thereby, the crown can be joined to the abutment with a self-aligning connection that prevents relative rotation between them. A screw, passed into the chimney opening, engages the tapped hole in the abutment so as to hold the crown axially to the abutment. Thus, the crown cannot rotate about the abutment because it is fixed into the special contours on the exposed abutment end, and the crown cannot pull away from the abutment when the screw has been tightened in place. Finally, the chimney above the screw is filled with a composite filler material that hardens and is shaped as part of the crown, to look like a natural tooth.
However, the problem, and a source of patient dissatisfaction, resides in the several months of marked inconvenience for the patient while the process of osseointegration takes place and the implant becomes fixedly attached to the jaw bone. This difficulty, to be overcome, requires an avoidance of eating and chewing foods that will cause undesirable stresses and force transmissions in the tooth region. From present understanding, it appears that osseointegration takes place between the bone and the titanium implant under strict conditions of immobilization and without force or stress applied on the bone/implant interface. An uninterrupted growth of bone on the titanium surface is the time-consuming factor. It is not completely clear at this time whether osseointegration taken place under the condition of extreme immobilization and, if not, how much movement of the implant is tolerable. It is also not clear whether controlled application of force is harmful, or may actually help if applied in a specific manner. From many years of metal implantation in bones, it has been learned that stress sharing constructions made of bone and implant encourage bone healing and bone growth, while stress shielding implants prevent healing, mainly by eliminating the stimuli from the body's osteoblasts. After a tooth extraction, it is necessary that the site should heal prior to initiating implant procedures. This further extends the time period until the patient is ready to resume normal chewing at the site.
What is needed is an implant system that provides effective attachment to the bone in a shorter period of time than present implants require, and with less inconvenience for the patient during the period when osseointegration takes place.
For example, the U.S. Pat. No. 5,542,847 describes the dental prosthesis implants placed into a socket formed in the jaw bone, is held in position by screws that pass through the jaw bone from the buccal cortical surface to the lingual cortical surface, and through the implant that is located between the cortical surfaces. Threads on the screw shank form and engage threads in the cortex on opposite sides of the jaw bone. The implant, when inserted in the socket and anchored by the screws, is strongly held to the jaw's bony structure. Stresses applied to a prosthetic device, e.g., a tooth crown that is attached to the implant, are substantially borne by the cortex by way of the screws.
Despite of strong connection, such implant installation requires additional alien subjects (e.g. the screws passing through the jaw bone from the buccal cortical surface to the lingual cortical surface) in the human (patient's) jaw, that is highly discomfortable and also requires longer time for the patient's recovery.
Another implants and the connecting device are disclosed in U.S. Pat. No. 4,746,293. The patent describes an implant with the individual crowns, preventing possible torsional forces from running up and disengaging the spacer screw with a milled groove in which a droplet of acrylate is applied for reversible locking. Generally, the implant and connecting device comprise an anchorage unit (a fixture) implanted in jawbone tissue. The spacer is provided with a central, cylindrical spacer screw designed specifically for this purpose with an extended, exteriorly threaded pin. The spacer is provided with a collar consisting of two surfaces: an outer horizontal surface and an obliquely inclined surface located inside the surface.
The anchorage unit and the outer prosthesis portion, a connecting device in the form of an outer, sleeve-shaped patrix is connected to the spacer. The outer circumferential surface of the patrix connects to the outer prosthesis portion and the patrix surrounds the central spacer screws. The base of the patrix is connected to the collarshaped portions of the spacer by the intermediary of a resilient member in the form of a rubber O-ring.
The obliquely inclined surface of the collar-shaped portion of the spacer forms, together with an upper horizontal surface 8 on a cuff of the spacer, two of the walls of an annular tunnel for the resilient member, namely the lower horizontal wall and the oblique lateral wall. The remaining walls of the annular tunnel viz. the medial, vertical wall and the upper horizontal wall are formed by the circumferential surface of the spacer screw, which in this case is of circular profile, and the planar, lower base surface of the patrix, respectively.
The annular tunnel of rhomboid cross-section which is formed by the above-mentioned surface is adapted to the resilient member in the form of an O-ring of rubber. The O-ring is dimensioned to permit a deflection of the order of magnitude of about 100-200 nu.m. In eccentric or oblique loading, this corresponds to a maximum angular displacement of 1°-2°.
The patrix surface is so disposed as to depress the O-ring and provide the contemplated elastic transmission of forces between the outer prosthesis portion and the spacer (the fixture). The play provided between the patrix surface and the spacer collar surface should exceed 200 nu.m in order to permit the planned elastic deflection of 100-200 nu.m.
The elastic connection is anchored (locked) by an interiorly threaded special nut manufactured of, for example, gold. The nut is screwed onto the exteriorly threaded pin of the spacer screw such that its lower peripheral end surface meets a horizontal heel on the patrix. The nut is screwed on so far that light compression of the O-ring is attained. This light compression or pre-tensioning may be exactly determined in that the screw which is disposed in the top of the nut is turned so as to register with a groove in the upper patrix edge. By provision of further two such groove markings in the patrix edge to which the screw slot can be turned, both moderate and hard pre-tensioning of the connecting device may be mode, depending upon the deflection amplitude which is deemed to be most purposeful in each individual situation.
The upper surface of the special nut may be covered with, for example, a gold washer once it has been locked by a droplet of acrylate. Acrylate is then applied over the gold washer in order to fill the aperture through which the nut was applied.
The implant with such connection is not sufficiently reliable considering the presence of the rubber O-ring.
Thus, there is a great need in the art for the improved not complex, not expensive and reliable molar and/or pre-molar dental implant embedded in the bone of a person's (a dental patient's) jaw.